Metabolic rate (article) | Khan Academy
case, the relationship will be a straight line, as shown on the figure on the next page. metabolic rate increases with body size, but not in a constant values in the table using the allometric values given, 2) calculate the times. Download scientific diagram | (a) The relation between body size and metabolic rate in hypothetical lineages originating from species of similar body size. 2; Table 1), exponents of (r2 = ) and (r2 = ) can be . Relationship between body mass (M, g) and basal metabolic rate.
Too much blood would be required. This intimates that as proposed and popularly handled, the equation does not have the relevance to biology claimed, and is based upon assumptions that are not part of the equation, like fractality. This term is a ratio of the efficiency of redox coupling between the biomass battery W, and the sources of chemical energy available to it, measured against loss to heat.
ME is therefore a ratio of amperes of anabolism to amperes of catabolism. Efficiencies like these are not found in nature unless thermogenesis is included as part of metabolic rate. This removes the WBE version of Kleiber's law, which the metabolic theory of ecology rests on, from any biological relevance whatsoever. The efficiency that is purported to be modeled is actually assumed. In plants, according to a paper in in Nature, the exponent of mass is close to 1.
The key problem is the nature of metabolic energy and the extent of what is considered metabolism. The problem is most clearly noticeable in the unit term for metabolic rate, i.
Calories are a measure of heat energy. This leads to the idea that thermogenesis is part of metabolism, Kleiber's original treatment, and rules out that metabolism is all about chemical energy, not heat energy.
The picture is further obfuscated when the idea of respiratory metabolism is introduced to refine and limit the definition of metabolism such that oxygen consumption and synthesis of ATP are its ultimate factors. Furthermore, glycogenesis is excluded from metabolic consideration on this model since glycogenesis is not included in the respiratory chain, and is itself a reduction reaction not strictly dependent upon the proximity of certain molecules and atoms delivered by capillaries and vibrating from Brownian motion.
Energy is required for glycogenesis, and the blood does not deliver energy, just the ingredients for endergonic reactions.
» How does metabolic rate scale with size?
The energy comes from redox coupling, what ME is all about. Metabolic rate becomes the rate at which a biomass recharges so that its degeneration is prevented, and its organization is perpetuated.
ME is here understood as a ratio of the rate of reduction reactions necessary for the maintenance, growth, replication and behavior of the biomass, to the rate of availability of energy captured and expended by that biomass. ME is a statement of redox coupling efficiency. ME excludes thermogenesis as part of metabolism, consequently.
The organism determines ME, and that ME is the same for it and for its cells. Other models taking into consideration how the energy is used, on the contrary, can accommodate thermogenesis as a part of the model.
Kleiber's law - Wikipedia
For example, a concept akin to the ME concept is the fraction f of the energy income that is not lost as heat. Thus, as the ME, it depends on the energy stored and lost during the synthesis and use of ATP, and hence on redox coupling. On the contrary, if f were 1, all the energy income would be used in metabolic work, thus being the metabolic scaling directly proportional to the number of cells, i.
Reader Mode When one arrives at biology from its sister disciplines of physics or engineering there is a strong temptation to search for consistent quantitative trends and general rules. One such pursuit centers on the power consumption of different organisms, the so-called metabolic energy consumption rate.
This example illustrates how scaling arguments work. For many inanimate systems the energy produced has to be removed through the bounding surface area, and each unit of area allows a constant energy flux.
At the same time the volume, V, scales as R3. Assuming constant density this will also be the scaling of the total mass, M. According to our assumption above, the energy is removed through the surface at a constant rate, and thus the total energy produced should be proportional to A, i.Energy Metabolism PART 4 Aerobic Metabolism and Body Size
Does this simple scaling result based on simple considerations of energy transfer also hold for biological systems? The resting energy demand of organisms has recently been compared among more than different organisms spanning over 20 orders of magnitude in mass! In contrast to the Kleiber law prediction, this recent work found a relatively small range of variation with the vast majority of organisms having power requirements lying between 0.
Further evidence for breaking of Kleiber scaling was provided recently for protists and prokaryotes J. The metabolic rate of an organism is condition dependent, and thus should be strictly defined if one wants to make an honest comparison across organisms. The most extreme example we are aware of is that bees in flight increase their oxygen consumption and thus their energy consumption by about fold in comparison to resting conditions BNID